Silk Manufacturing Process Sakunthala Athukorala Ag/07/012
Silk Manufacturing Process Silk is a natural protein fiber produced by certain caterpillars in orderto encase themselves in the form of cocoons. Silk has set the standard inluxury fabrics for several millennia. The origins of silk date back toAncient China. Legend has it that a Chinese princess was sipping tea in her gardenwhen a cocoon fell into her cup, and the hot tea loosened the long strand of silk.Ancient literature, however, attributes the popularization of silk to the ChineseEmpress Si-Ling, to around 2600 B.C. Called the Goddess of the Silkworm; Si-Lingapparently raised silkworms and designed a loom for making silk fabrics. Themaking of silk is different from that of other natural fibers. There are many stepsinvolved in silk manufacturing. Cultivation of Cocoons ( Sericulture) Filature Operations Manufacturing of Silk Yarns Finishing of Silk FabricsManufacturing Process for Silk YarnsSilk is a fine translucent fiber produced from the silkworm. The manufacturingprocess of silk starts with the rearing of cocoons. There are many varieties of thesilkworm from which the silk fiber can be obtained. However, it is found that thefiber obtained from the larva of Bombyxmori is of commercial value. The process ofobtaining silk fiber from Bombyxmori requires careful nourishment of the cocoonswhich is put through the spinning process.Cultivation of Cocoons:The process of cultivating the silkworm for the production of raw silk is called assericulture. Silk fiber is a continuous filament fiber consisting of the fibroin, which isconnected together with the silk gum, sericin. This natural protein or fibroin issecreted from two salivary glands.
There are four stages in the life cycle of the moth which are as follows: 1. The egg, which develops into a larva, or caterpillar – the silkworm 2. The silkworm, which spins its cocoon for protection, to permit development into the pupa 3. The pupa emerges from the cocoon as the moth. 4. Female moth lays eggs, so continuing the life cycle. They may be hatched three times a year. The female moth lays around 350 to 400 eggs and the moths die soon after. As they are subject to hereditary infection, the eggs from infected moths are destroyed which results into production of fine silk. Larvae of about 3mm are hatched from the eggs. For about 20 to 30 days, they are carefully nurtured and are fed five times a day on chopped mulberry leaves. Ideal temperature 23c-27c, humidity is 65%-80%.The silk moth lays eggs,
The flowing pathway is used to the production of silk fiber: Sexing Silk of moth caterpillars has been used for textile manufacture. When sexing pupae are used by identification of male and female pupae by looking at the back. Have to do sexing on 8th day after pupation. Then cut the cocoon do not separate cut top, and then place the cocoons in a box like drawer. Cover the box with tissue paper and two boxes separate male and female. Mating The silk-moths cannot fly because their bodies are too heavy in relation to their wings. Male’s silk-moths die soon after mating while one single female silk-moth lies from 300 to 500 tiny eggs before she dies. The eggs hatch into the silkworms in spring time and the complete cycle takes approximately about two months. In 11thday, just after emergence mating with male and female by both are coupling. Mating for about one day every 30 minutes ejaculate sperms. Silk-worms Moths Mating
Decoupling After 1 ½ hours. Because need three ejaculations.Egg laying Silk moths lay eggs on specially prepared paper by using paper card method. Laying eggsChemical treatment of eggs I) Formaldehyde treatment (2%)-When immersing eggs are disinfected. II) Acid treatment (1.1 5g Hcl)-eggs are immersed for 5 minuets III) Washing in running water IV) Air drying-keeping under the fanIncubation I) 1st day to 7thkeep the eggs rapped in a tissue paper. II) 8th day-black boxing, eggs are rapped with black paper or put in to black box to prevent irregular hatching.Hatching 11th day morning all the eggs are gray in color with dark spot. Expose eggs to light and then eggs are hatched around an hour. Silkworm are white but this stage black in ant stage .Which hatch into an ant called as larva about 1/8 inches (3mm) in length. This can be done at breeding station or rearing station.
Brushing Keep the eggs cards are rearing trays and removal of warms from egg shells/cards. Then giving 1stfeed (1cm strips of lender mulberry leaves).warms are very attractive to mulberry leaves because it contain citral.Warm rearing stationI) feedingII) CleaningIII) Increasing spaceFeeding the larva The larva at this stage has voracious appetite and requires careful nourishment. They are fed 5 times a day on chopped mulberry leaves. After four changes of skin or molting the worm reaches full growth of about 3 ½ inches (9cm) long. At this stage the interest in the food ceases and is ready to spin its cocoon. The silkworm begins to secrete a protein like substance through a small opening under the caterpillar’s jaws which is called as the spinneret. The silk solidifies when it comes in contact with the air.
On 3rd day, 20000 warms need 0.8 square meters.Stop feeding for about day 20 hours need molting.4th day do not feed even feed even feed they do not eat. End of the 3rdmoultingmanagement and maintain low RH.5th day-2nd instars-spacing gradually increase.7th day -molting management8th day-3rdinstar,increasespace,feeding mature leaves and cleaning11th day -molting12th day-4th instars16th day-molting17th day-27th day-5thinstar, branch feeding. This called flour rearing or tablerearing. Early silkworms mature silkworm’s larvaePupation-On 27th day they leave the leaves and look for a corner to build acocoon. Within twenty – four hours and in three days the cocoon is complete to asize and shape of a peanut shell.The filament is in the form of a double strand of fibroin, which is held together bya gummy substance called sericin, or silk gum.As this cutting through damages the cocoon, the filament cannot be unwound inone long thread. The life cycle is terminated at this point by a process known asstoving, or stifling.If left undisturbed, the pupae inside the cocoon develop into a moth within twoweeks. To emerge, the moth breaks open the cocoon by secreting an alkalineliquid that dissolves the filament.
Processing & grading The silk yarn production begins with selecting for their quality. The cocoons will be sorted into normal and abnormal cocoons. The fresh cocoons normal are reelable to produce raw silk but the abnormal cocoons are unreelable. The abnormal cocoons are double cocoons, perforated cocoons, internally and externally soiled cocoons, thin-end cocoons, thin-middle cocoons, malformed cocoons, etc.After the first selection of cocoons, They have to be dried. The first goal of cocoon drying is the protection of cocoon quality, to preserve conditions for reeling cocoons and prevent damage that might be caused by long periods of storage. Drying kills the pupa and evaporates moisture that would otherwise ruin cocoons. Dried cocoon storage conditions are designed to keep the raw material for long periods without any damage from moulds and pests. Cocoon storage should preferably be built with double walls. Cloth or polyethylene bags are recommended as containers for dried cocoon storage. In most modern factories which aim at producing high-grade raw silk, the cocoons are graded on visual inspection or by mechanical tests are actually mixed as in the required proportions. This is called cocoon mixing or blending and is done to ensure speed and uniformity of reeling as well as to obtain the desired effect in raw silk. The reelable cocoons have then to undergo the reeling processing, after which they are either processed further to raw silk or to thrown silk. The unreelable silk is processed further to spun silk.
The technological process of silk reeling. Technological process for silk reeling. The End